For each A from 0 to Total Day.
+1 to Day Name Changer.
If that's the trigger you used, this explains it. Say that its day 5. The trigger will cycle through the action list for the "For then" 5 times, so the TotalDay value will go up +5 instead of +1.
At the start of a new day:
Modify TotalDayNumber +1
If DayNameNumber = 7, then set DayNameNumber = 1, else modify DayNameNumber +1
If DayNameNumber = 1, then DayName = "Monday", etc. Using a switch case action should work here too.
If that's the trigger you used, this explains it. Say that its day 5. The trigger will cycle through the action list for the "For then" 5 times, so the TotalDay value will go up +5 instead of +1.
Are you sure that the action isn't being fired multiple times by mistake?